Hydraulic fracturing and horizontal drilling has helped increase the hydrocarbon production from shale reservoirs in the last ten years. Higher initial production rates are achieved in the shale oil wells with the existing technology, however, reservoir pressure declines rapidly. Final oil recovery of the shale reservoirs remains only about 5% to about 10% of the original oil in place (“OOIP”).
Water flooding cannot be used for the pressure maintenance in shale reservoirs due to the lower injectivity of water into such low permeable formations. Gas injection has been considered as a secondary recovery method in shale reservoirs due to the higher mobility of the gas; however, an unfavorable mobility ratio of gas to oil causes viscous fingering and leaves large quantities of un-swept oil in the reservoir using conventional gas floods.
Common enhanced oil recovery (“EOR”) surfactants are non-volatile. Surfactants such as dodecylbenzene sulfonic acid and its salts list the boiling point of sulfuric acid, an impurity, as the lowest value for the mixture at 554° F. (290° C.). Ethoxylates such as the ethylene oxide/propylene oxide (“EO/PO”) block copolymers have such high molecular weights that they decompose rather than have a normal boiling point on heating.